The invention relates to a self-propelled harvesting machine, such as a forage harvester or a combine harvester. Harvesting machines generally comprise an intake assembly, which includes a front attachment that can be replaced depending on the crop and, a processing assembly, which comprises at least one chopping or threshing mechanism.
In order to ensure a high and constant quality of processing via the processing assembly, it is desirable to have the capability to feed a stream of crop having an unvarying thickness to this processing assembly. To this end, it is known to regulate the forward speed of the harvesting machine in a manner that is inversely proportional to the stand density of the crop on the field. Difficulties arise with such known operation, however, when the density of the stand to be harvested temporarily fluctuates. For example, when the harvesting machine suddenly enters a region having a high stand density, the crop throughput in the intake assembly may increase, before the forward speed can be adjusted. The processing assembly therefore becomes unable to handle the crop throughput. In a case of a forage harvester in particular, such operation can cause the engine to stall. In a case of a combine harvester, the result can be that a large proportion of non-grain material reaches the grain tank or, that a large quantity of grain is separated out with chaff and stalks or both.
In order to be able to react to fluctuations in the stand density, it is desirable per se to detect these fluctuations at an early point in time, namely (if possible), before the harvesting machine enters the region having a high stand density. Doing so could ensure that the forward speed can be adjusted in a timely manner. Detection of this type, however (which is necessarily contactless), is highly unreliable. One example is known from EP 1 271 139 A2. High costs of this technology have so far stood in the way of the widespread implementation of the technology.